1. Field of the Invention
The present invention relates in general to a radiation thermometer adapted to measure a temperature based on a radiant energy produced by an object, and more particularly to a radiant-energy responsive temperature measuring apparatus of a scanning type wherein a plurality of light-sensitive elements responsive to the radiant energy from the object are disposed in a straight line.
2. Discussion of the Prior Art
As a radiation thermometer responsive to radiant energy produced by an object to be observed, there is known a radiant-energy temperature measuring apparatus of a scanning type indicated above. Generally, this type of radiant-energy responsive temperature measuring apparatus incorporates a light-sensitive device which has a linear array of plurality of light-sensitive elements which are responsive to respective amounts of radiant energy produced at different points of the object arranged on a straight line, and which generate photoelectric signals whose levels correspond to the respective amounts of radiant energy received. The measuring apparatus further incorporates a device for determining temperatures of the object, according to the photoelectric signals generated from the light-sensitive elements of the light-sensitive device.
In this scanning type of radiant-energy temperature measuring apparatus, the temperature of the object at the desired one of the different points on a straight line can be measured by supplying the temperature determining device with the photoelectric signal from the corresponding one of the light-sensitive elements which optically matches the desired point on the object. For example, where the object is a steel material which is fed in a predetermined direction for a hot-rolling process, the measuring apparatus is capable of continuously measuring the temperature of the material at a desired point thereof that is selected in a direction of width of the material perpendicular to its feeding direction.
Thus, once the point of measurement of the temperature has been determined, the corresponding light-sensitive element whose photoelectric signal is applied to the temperature determining device is determined and fixed. Therefore, if the relative position between the scanning type radiant-energy temperature measuring apparatus and the object is changed, or deviated from the predetermined relation, the apparatus fails to accurately measure the temperature of the object at the selected point. In the above case wherein the object is moved in one direction while the measurement point is selected in the direction perpendicular to the moving direction, as described above, the position of the moving object tends to be varied in the above perpendicular direction, due to possible vibration of the object, whereby the actual point of measurement may be deviated from the predetermined desired point.